Obstetric stethoscope

ABSTRACT

A light-weight obstetric stethoscope comprises, a binaural construction having a pair of legs and an interconnecting bight section, said legs being resiliently urged toward a normal untensioned position against deforming forces at least in part by the characteristics of the material of fabrication, the free ends of said legs forming ear tubes; ear plugs engaging said ear tubes; a tubular stem extending from said bight; and audio pickup means attached to said stem, whereby when said ear plugs are in the user&#39;&#39;s ears, said bight section is adapted to rest on the user&#39;&#39;s chin, said stem projecting outwardly therefrom.

United States Patent 91 Littmann [45 May 29, 1973 [54] OBSTETRIC STETHOSCOPE [73] Assignee: Minnesota Mining and Manufacturing Company, St. Paul, Minn.

[22] Filed: July 21, 1971 [21 Appl. No.: 164,623

Related US. Application Data [63] Continuation-impart of Ser. No. 30,897, April 22,

1970, abandoned.

[52] US. Cl ..18l/24 [51] Int. Cl. ..A61b 7/02 [58] Field of Search ..181/24; 179/1 ST; l28/2.05 S

[56] Reierences Cited UNITED STATES PATENTS 2,335,711 11/1943 Tregilgas ..l81/24 3 ,314,499 4/1967 Blackman ..l81/24 3,437,172 4/1969 Allen ..l8l/24 3,515,239 6/1970 Machlup et a1 "181/24 FOREIGN PATENTS OR APPLICATIONS 1,556,332 12/1968 France ..l79/1 ST Primary Examiner-Stephen J. Tomsky Attorney-Kinney, Alexander, Sell, Steldt & Dlahunt [57] ABSTRACT A light-weight obstetric stethoscope comprises, a binaural construction having a pair of legs and an interconnecting bight section, said legs being resiliently urged toward a normal untensioned position against deforming forces at least, in part by the characteristics of the material of fabrication, the free ends of said legs forming ear tubes; ear plugs engaging said ear tubes; a tubular stem extending from said bight; and audio pickup means attached to said stem, whereby when said ear plugs are in the users ears, said bight section is adapted to rest on the users chin, said stern projecting outwardly therefrom.

5 Claims, 7 Drawing Figures PATENTEUHAYEQISYS sum 2 of 2 FIG. 6

l N VEN'TOR. DA v/0 L I T TMA NN A TTORWE Y3 OBSTETRIC STETI-IOSCOPE This application is a continuation-in-part of copending application Serial No. 30,897, filed April 22, 1970, now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to an obstetric stethoscope adapted to rest on the users chin so as to not obstruct his line of vision. More particularly, the present invention relates to an extremely lightweight comfortable obstetric stethoscope comprising a binaural construction having a pair of legs and an interconnecting bight section, a rigid or nearly rigid tubular stem engaged with and extending from the bight, and audio pickup means attached to the stem, the bight section being adapted to rest on the users chin with the stem projecting outwardly therefrom.

The obstetric stethoscopes presently commercially available are designed in such a way so that they may be worn on the head of the physician freeing his hands to perform tasks related to childbirth. The obstetric stethoscope most commonly used at present is the type employing a head piece attached to a rigid stem such that the stem extends directly outwardly from the users forehead. An auditory sound receptive horn is attached to the othenend of the stem. Rubber connecting tubes are attached to the rigid stem near the horn and have ear pieces on the other end of the tubes. These tubes hang downwardly from the rigid stern until reaching approximately the chin area of the user, at which point they turn toward and are engaged with the ear.

The obvious disadvantage of this type of an obstetric stethoscope is that the connecting tubes remain in the user's line of vision, at least partially impairing his view of the working area. Further, the prior art one-piece stethoscopes are not easilydisassembled and cannot be conveniently carried by the physician and, are of such a weight that the discomfort caused from their use has prompted many obstetricians to give up using such stethoscopes altogether. Thus, there is a substantial need for a lightweight, comfortable obstetric stethoscope which may be conveniently disassembled so that it may be carried with the physician and one which does not impair the line of vision of the user.

SUMMARY OF THE INVENTION According to the present invention there is provided an obstetric stethoscope which is readily adapted to fit on the users head so that no portion thereof is in a position to impair the line of vision of the user. Further, the stethoscope is of a very lightweight material for the comfort of the user, and is adapted such that it may be disassembled and conveniently carried in the pocket of the user when not in actual use.

The obstetric stethoscope of the present invention comprises, generally, a binaural construction having a pair of legs and an'interconnecting bight section, said legs being resiliently urged toward a normal untensioned position against deforming forces at least in part by the characteristics of the material used to fabricate the stethoscope, the free ends of the legs forming ear tubes; ear plugs engaging said ear tubes; tubular stem extending from said bight section and in fluid communication therewith; and audio pickup means attached to the stem, whereby when said ear plugs are inserted into the users ears, said bight section is adapted to rest on the users chin, said stem projecting outwardly therefrom.

In a modified form of the invention, the legs of the binaural are integrally connected to a resilient yoke which functions in part as a spring member to maintain the legs of the binaural in a generally U-shaped configuration. In the preferred embodiment of the present invention, a T-shaped yoke is threaded onto an elongated resilient, tubular member. The member is bent and set into a U-shaped configuration having two legs and a bight, the bight portion formed of a homogeneous mass, with one leg and an adjacent portion of the bight lying substantially in one plane and the other leg and its adjacent portion of the bight lying in a second plane intersecting the first preferably at an angle of substantially 15. A hole is formed in the bight aligned with the stem of the yoke and a retaining pin may be then forced through the stem and into the hole. A rigid tubular stem, having an auditory horn thereon, is engaged with the stem of the yoke. In a modification of the invention, the U-shaped tubular member may be reformed with its legs in a cross-over position. And while in this position, a yoke is formed on the bight portion of a resilient material capable of normally retaining the legs in this cross-over position. The yoke is formed with two legs molded over the bight and a stem having an opening extending longitudinally through it extending away from the center portion of the bight with the opening of the stem in fluid communication with the opening of the legs.

The objects and advantages of the present invention will be more clearly understood when considered in conjunction with the accompanying drawing in which:

FIG. 1 is a perspective view of the stethoscope of the present invention showing its position when in use;

FIG. 2 is a perspective view of the obstetric stethoscope illustrating a preferred embodiment of the invention;

FIG. 3 is aside view of the obstetric stethoscope in fragmentary cross section;

FIG. 4 is a cross-sectional view taken along the line 4-4 of FIG. 3;

FIG. 5 is a perspective view, with partial cross section, of one embodiment of the obstetric stethoscope having an adjustable chin rest;

FIG. 6 is a perspective side view of the stethoscope of FIG. 5; and i FIG. 7 is a cross section taken along lines 7-7 of FIG. 6.

Referring to FIG. 1 there is illustrated an obstetric stethoscope having a binaural portion 11 comprised of an elongated tubular homogeneous mass of plastic material having ear plugs 12 and having a stem 18 attached thereto and extending outward therefrom, the stem 18 being held to the binaural by means of a yoke 25. The stem is fitted with a horn 20 for auditory reception.

Preferably, the entire binaural construction hereindescribed is made of a synthetic organic plastic material with the plastic material normally being nondeformable but flexible and resilient. The use of plastic eliminates the need for springs and other expensive metal components. Further, the use of plastic allows the stethoscope to be very light and comfortable, the entire stethoscope weighing only about 1 ounce. A variety of suitable plastics may be used provided they impart the desired physical characteristics to the binaural.

A suitable class of plastics includes, for example, plastics in the polypropylene family. Similarly, the stem is made of a synthetic, organic plastic material with the plastic material, however, normally being nondeformable but relatively rigid so that the stem will continually retain an outwardly extending position with relation to the users chin. Other materials, however, such as metal, may be used to fabricate the binaural, the stem, or both.

With reference to FIGS. 2 and 3, the binaural portion of the obstetric stethoscope of the present invention consists primarily of legs 14 and 15 with a continuous and inter-connecting bight section 24. The legs 14 and 15 and bight 24 are preferably formed of an extruded polypropylene tubing which is bent by known means, on application of heat, into the shape generally described herein. In this arrangement, the free ends of the legs 14 and 15 are bent respectively into ear tubes 22 and 23. The ear tubes 22 and 23 extend generally at a 15 angle from the major plane of the stethoscope. The major plane of the stethoscope is defined for purposes of this disclosure as the plane of a flat surface upon which the stethoscope rests when laid on the surface in the position illustrated in FIG. 3.

The tubular members 14 and 15 are formed, preferably with a wall having a non-uniform thickness. In the preferred embodiment, the wall thickness, which is illustrated in FIG. 4, has a major axis 26 and a minor axis 27 extending at right angles to one another. The major axis preferably should be in the order of magnitude of 50-100 percent greater than the minor axis, and in the preferred embodiment the major axis 26 should have a length of about 0.320 inches and the minor axis of 0.190 inches. The hole or aperture 19 that extends longitudinally through the tubular member is preferably circular in cross section and has a diameter in the order of magnitude of about 30-40 percent of the major axis. In a specific embodiment, the diameter of the aperture 19 is in the order of magnitude of about one-eighth inch.

The yoke 25 is preferably formed of an injection molded relatively rigid plastic having sufficient structural rigidity to withstand substantial stress and may be made of a wide variety of materials including, for example, polypropylene plastic. The yoke 25 is formed with relatively short legs 16 and 17 connected integrally to its stem 28 with the legs 16 and 17 having a passage in fluid communication with the passage through the stem 18. The cross sectional configuration of the passage through the legs 14 and 15 conforms to the outer cross sectional configuration of the bight 24. The bight 24 snugly fits within and extends through legs 16 and 17 of yoke 25. The opening in the bottom of the bight 24 connects the interior of legs 14 and 15 with the passage through the stem 18. Extending past the stem 28 of the yoke 25 is a small portion 37 adapted to be threaded into the rigid stem 18 leaving a slightly visible juncture at 30.

The tubular stem 18, which may be of any convenient length, is connected at its other end to an audio pickup means or horn 20. The horn may or may not have a rubber piece 21 protecting the end thereof. The car tips 12 and 13 are formed of an angular wall about a passage. The passage has a section which is oval in crosssectional configuration and is dimensioned to fit snugly about the ends of the legs 14 and 15 in frictional engagement. The outer surface of the car tips should be shaped to conform with the outer portion of the wearers ear canal.

The stem 18 is fabricated from a relatively rigid material, preferably plastic, an example of which is polypropylene. The stem may be fabricated in sections as illustrated in the drawing to permit disassembling of the stethoscope so that the user may place it in his pocket and carry it with him. As the prior art stethoscopes are of one piece, the user has no convenient way to carry the stethoscope with him.

The stem 18, in the embodiment illustrated in the drawings, is made in three sections. Thus, the length of the stem may be varied to suit the personal requirements of the user. More sections may be added if a relatively long stem is desired, as for example, when the user does not care to bend over to any great extent or where such movement is impaired by physical incapability. The sections are designed so as to have female and male threaded portions wherein each portion may be conveniently threaded onto the next portion when the obstetric stethoscope is to be used. These threaded positions are illustrated as 37, 36, 35, and 34, the latter being threaded into the audio pickup means or horn 20. When the sections are threaded together, there remains only slightly visible junctures at 30, 31, 32, and 33. Although such threading is preferred, the sections may also be held together by frictional engagement or other suitable means.

,The audio pickup means or horn 20 may be of any type presently used on a stethoscope, the horn configuration as illustrated in the drawings being preferred. The horn 20 is preferably made from a suitable plastic because of its non-chilling properties, although various other materials may be used to fabricate the horn, such as metal. A rubber or plastic protective rim 21 may be placed over the end of the horn 20 to insure the nonchilling properties of the horn for the patients comfort, particularly where metal is used. The horn 20 is threaded in a manner to receive and engage the end 34 of stem 18. The horn may also be attached by other means such as frictional engagement.

The obstetric stethoscope illustrated in the drawings may be fabricated utilizing a suitable jig or mold. In the fabrication of the stethoscope a length of tubing preferably extruded of polypropyleneand having the cross sectional configuration illustrated in FIG. 4 is cut to a selected length, as for example, l7% inches. This tubing is then heated to a temperature sufficient to render it workable. If the material of which the tubing is formed is polypropylene, it may be preheated to a temperature of approximately 200 F. At this temperature the tubing is softened to the extent that permits it to be flexed or bent but does not close the longitudinal hole extended through it. After the tubing has been cut to a satisfactory length, a yoke 25 is threaded onto this straight tubing and is centrally located with respect to it. The yoke is threaded onto the tubing so that its stem 22 extends perpendicularly from the major axis 26 of the tubing. After the tubing has been fitted into the position in which it is to be held by the mold, it is cooled. A hole is then drilled in the tubing through the opening of the stem 28 of the yoke 25 to complete a fluid con nection between the interior of the arms 14 and 15 and the passage of the stem 28. The straight rigid tubular stem 18 may then be threaded onto the pre-threaded stem 28 of yoke 25 and the horn 20 threaded onto the outer end of the stem 18.

The binaural portion of the stethoscope is formed with the free ends of its legs 14 and 15 close to or substantially touching each other when in a normal, untensioned position. It has been found that by proper selection of the material of which the tubing is formed, this shape provides adequate tension when the free ends are separated for placement in the wearer's ears. If desired, however, the techniques herein illustrated may be utilized to form a stethoscope in which the legs overlap.

The present invention also contemplates fabricating an obstetric stethoscope having a binaural portion with a yoke that is attached after the binaural has been shaped in the manner as previously described. In such an arrangement, the yoke is formed of mating pairs which are attached to the bight of the binaural tube after the tube has been shaped.

Turning now to FIG. 5 and 6, there is illustrated one preferred embodiment of the present invention. In this embodiment the obstetric stethoscope has an adjustable chin rest 46 slidably, removably attached to stem 52 by means of a retainer ring 50. By adjusting the chin rest, the stethoscope can be modified to fit essentially any facial configuration or personal preference. The yoke member 41 is a flexible tubing cemented to legs 14 and 15 to prevent air leakage which leakage often has a deleterious effect on the quality and the amount of sound received by the physician or nurse. The flexible tubing is preferred because it allows for angulation of the instrument when in use. The flexible, pliable bight section 40 is reinforced with a spring member 42. Thus, a restrained flexibility at the yoke is provided to permit separation of and spring tension on the ear tips 12 and 13, and further, angulation of the instrument on the users chin which aids in positioning of the horn 20.

A pliable connecting portion 60 is attached to the rigid stem 18 by a metal tubular housing 52. The metal housing 52 is attached to the rigid stem 18 in a manner described hereinafter. The flexible tubing preferably has an outside diameter only slightly less than the inside diameter of the metal housing 52 to insure good contact and air impermeability therebetween and is better illustrated in FIG. 7. The tubing 60 (connecting the yoke to the rigid extending portion) is bonded to the metal housing 52 at 61 along approximately 1% to 2 inches along the length dimension of the stem. The flexible tubing is preferably cemented to the metal housing. Thus, the chin rest 46 is movable on the outer surface of the metal housing while the flexible tubing is fixedly cemented inside the metal housing.

The prevention of air leakage is important to insure high quality of sound through the device. To further insure that there is no leakage of air, a portion of the flexible tubing 62 extends into a slight indentation formed by providing a lip 64 on the inside diameter of the metal housing 52. The snug fit of the flexible tubing between lip 64 and the remainder of the metal housing insures an air tight seal so that the only passage of air through the stem is through the aperture 68. The metal housing 52 may then be threaded (at 66) onto the inexpensive, light plastic extending portion 18.

The metal housing is preferably used as an intermediate between the flexible tubing and the plastic rigid portion to serve as a sliding surface for the adjustable chin rest 46 and help prevent air leakage and also allows for a good friction fit between the stem 52, the sliding portion of the chin rest 46 and the retainer ring 50. Various other materials could be used, however,

provided that the material would present a slidable surface to the sliding portion of the adjustable chin rest and would hold up during adjustments of the chin rest for a period of time. The entire stem, in fact, could be made of plastic.

The adjustable chin rest enables the physician to fit the obstetric stethoscope precisely to his face (particularly to his chin) and provides a three point selfretention of the instrument between the two ears and the chin. The chin rest is held against the chin by the pressure placed on the chin rest by the legs 14 and 15 which are held at the cars by ear plugs 12 and 13. The flexible tubing allows flexibility and the rigid stem can be moved and positioned at an angle from the chin while the chin rest remains relatively stationary on the chin. When the instrument is placed on the head of the physician, the stern and horn may be positioned and moved without the use of the hands, a maneuver which is normally required by obstetricians in auscultating for fetal heart sounds. Being firmly fixed and resting against the chin, by rest portion 48, sounds may also be carried by bone conduction through the chin rest, in addition to air conduction through the hollow tube, to provide two receptive areas for the heart sounds.

The adjustable chin rest 46, with the chin contacting portion 48 thereon, is removably attached to the metal housing 52 by retainer ring 50. Because of the various configuration of the users face and chin, it is preferred that the chin rest may be adjusted to fit the users requirements. To do this, the retainer ring 50 is merely slipped off the adjustable chin rest 46 and the chin rest adjusted to a length which would be comfortable to that particular user. When the rest is in the desired position, the stethoscope may be held in the fingers, at the gripping portion 54, for example, and the retainer ring 50 may then he slipped back over the contacting portions of the adjustable chin rest and held in place against the stem by a friction fit. Various retaining means may be used as long as they would permit adjustment of the chin rest.

The remainder of the rigidly extending stem is fitted together as hereinbefore discussed (e.g., at 32) for the insertion of segments to length or shorten the rigid stem. A removable pickup means or horn 20 is attached to the rigid stem. In the preferred embodiment, the stem allows for about 2 inches of movement of the slidable chin rest on the stem. Although 2 inches of movement would generally be sufficient to cover the various facial configurations involved, such length movement may not be sufficient. If this is the case, the stethoscope may be modified to have a chin rest which is capable of more than 2 inches of movement or the legs 14 and 15 of the stethoscope may be modified in length to accommodate the user.

The slidable chin rest, at least the sliding portion 46, is preferably fabricated from a metal. More preferred is stainless steel of a steel spring quality having a thickness of about l0 mils. The chin contacting portion itself 48 is preferably made out of a soft, cushioning, comfortable material such as rubber. Plastic is preferably used for the remainder of the stem as it enormously reduces the weight of the stethoscope which is a distinct advantage to the user who may carry one with him throughout the day.

In another embodiment of the stethoscope of the invention having an adjustable chin rest, various other materials could be used to form that portion of the stem 52 which holds the slidable portion of the chin rest 46. An example of such a material would be soft latex where the adjustable portion of the chin rest is actually inside the stem to prevent leakage. Thus, the chin rest would be slidable inside of the stem rather than outside as illustrated in the preferred embodiment.

What is claimed is: l. A lightweight obstetric stethoscope comprising: a binaural construction having a pair of legs and an interconnecting, flexible, tubular bight section; spring means in said bight section andattached to said legs, urging said legs toward a normal untensioned position against deforming forces, the free ends of said legs forming ear tubes; ear plugs engaging said ear tubes; a rigid tubular stem extending from said bight and in fluid communication therewith; an adjustable chin rest slidably, removably attached to said stem and extending beyond said bight section to a position between said legs; means to slidably, removably hold said chin rest on said stem; and

audio pickup means attached to said stern;

whereby when said ear plugs are in the users ears, and said chin rest is adjusted to rest on the user's chin said obstetric stethoscope is supported by a three point contact formed by the chin and the ears, said stem being flexibly movable so that it may be positioned by the user.

2. The stethoscope of claim 1 wherein said flexible tubular bight section is rubber.

3. The stethoscope of claim 1 wherein said stem is said flexible tubing extending into said metal section. 

1. A lightweight obstetric stethoscope comprising: a binaural construction having a pair of legs and an interconnecting, flexible, tubular bight section; spring means in said bight section and attached to said legs, urging said legs toward a normal untensioned position against deforming forces, the free ends of said legs forming ear tubes; ear plugs engaging said ear tubes; a rigid tubular stem extending from said bight and in fluid communication therewith; an adjustable chin rest slidably, removably attached to said stem and extending beyond said bight section to a position between said legs; means to slidably, removably hold said chin rest on said stem; and audio pickup means attached to said stem; whereby when said ear plugs are in the user''s ears, and said chin rest is adjusted to rest on the user''s chin said obstetric stethoscope is supported by a three point contact formed by the chin and the ears, said stem being flexibly movable so that it may be positioned by the user.
 2. The stethoscope of claim 1 wherein said flexible tubular bight section is rubber.
 3. The stethoscope of claim 1 wherein said stem is plastic.
 4. The stethoscope of claim 1 additionally having a tubular metal section bonded to and connecting said bight section with said stem, said metal section forming a part of said stem and presenting an outer sliding surface for said chin rest.
 5. The stethosCope of claim 4 wherein said tubular metal section has a lip located on the inside diameter of said section, said lip serving to hold an extension of said flexible tubing extending into said metal section. 